When developing new material, especially heat conductive material, the heat conductivity of the material needs to be measured. When designing a heat dissipation device for electronic devices, the designer needs to know the heat conductive capability of the material of the heat dissipation device. Precisely measuring beat conductivity of the material is the key of the design.
Conventionally, the heat conductivity of a material is measured via sandwiching a specimen made of the material between a heat source and an object with a lower temperature. The heat generated by the heat source flows through the specimen to the object with lower temperature. A temperature gradient ΔT exists between two opposite ends of the specimen. The distance between the two opposite ends of the specimen ΔX can be measured. Assuming that all of the heat generated byte heat source flows through the specimen, the heat energy Q of the heat flow flowing through the specimen is equal to the heat energy Q′ generated by the heat source. The heat energy Q′ generated by the heat source is calculated according to the following equation:Q′=αI2R
wherein R is the resistance value of a thermoelectric resistor embedded in the heat source, I represents the electric current flowing through the thermoelectric resistor, and α is a ratio of electrical power converted to heat energy of the thermoelectric resistor. The heat conductivity K of the material of the specimen can be calculated according to the following equation:K=q*ΔX/ΔTwherein q represents heat flow, which is the rate at which heat energy Q flows through the specimen per square meter, measured in W/m2.
In the above method, the specimen firmly contacts one face of the heat source. The other faces of the heat source are heat insulated by a layer of insulation material covered thereon in order to ensure all of the heat generated by the heat source flows through the specimen. However, the insulation capability of the insulation material, such as alumina, is limited. Some of the heat generated by the heat source is inevitably dissipated through the other faces which do not contact the specimen. That means, the measured heat energy Q of the heat flow flowing through the specimen is not equal to the actual heat energy Q′ generated by the heat source. Because the value of the heat energy Q of the heat flow flowing through the specimen is defined to be equal to the value of the heat energy Q′ generated by the heat source, the measured heat energy Q is inaccurate. This results in the calculated heat conductivity K of the material of the specimen being inaccurate.